1. Field of the Invention
The present invention relates to an electromagnetic wave shielding filter, a method of manufacturing the same and a plasma display panel (“PDP”) apparatus including the same. More particularly, the present invention relates to an electromagnetic wave shielding filter which has low electric conductivity, high visible light transmittance and good durability, a method of manufacturing the same and a PDP apparatus including the same.
2. Description of the Related Art
As modem society becomes more information-oriented, photoelectronic devices and apparatuses are advancing and are becoming more widespread. In particular, image display devices are being widely used in a variety of applications, including TV screens, monitors of personal computers, etc. Wide screens and a thin build have become the mainstream technology along with the progress of high performance image display devices.
The plasma display panel (PDP) is gaining popularity as a next-generation display device to replace the CRT because a PDP is thin and a large screen can be readily fabricated with a plurality of units. A PDP apparatus includes a plasma display panel on which an image is displayed using a gas discharge phenomenon, and exhibits superior display capabilities, including high display capacity, high brightness, high contrast, clear latent image, a wide viewing angle, etc.
In a PDP apparatus, when a direct current (DC) or alternating current (AC) voltage is applied to electrodes, a discharge of gas plasma is created, resulting in the emission of ultraviolet (UV) light. The UV emission excites adjacent phosphor materials, resulting in electromagnetic emission of visible light.
Despite the above advantages, PDPs face several challenges associated with driving characteristics, including an increase in electromagnetic wave radiation, near-infrared emission, and phosphor surface reflection, and an obscured color purity due to orange light emitted from helium (He) or xenon (Xe) used as a sealing gas.
The electromagnetic wave and near-infrared ray generated in PDPs may adversely affect human bodies and cause malfunction of precision machines such as wireless telephones or remote controllers. Thus, in order to make use of such PDPs, there is a desire to reduce the electromagnetic wave and near-infrared ray emitted from the PDPs to a predetermined level or less. In this respect, various PDP filters have been proposed for shielding electromagnetic waves or near-infrared rays emitted from the PDPs, reducing reflection of light and/or enhancing color purity. The proposed PDP filters are also required to meet transmittance requirements because the filters are installed on a front surface of each of the PDPs.
In order to reduce the electromagnetic wave and Near-Infrared Ray (NIR) emitted from plasma display panels to a predetermined level or less, various PDP filters have been used for the purposes of e.g., shielding electromagnetic waves or NIR emitted from the PDPs, reducing reflection of light and/or enhancing color purity. High transmittance is required for such filters because they are generally applied to the front surface of PDPs. Typical electromagnetic wave shielding filters meeting such requirements and characteristics are classified into a metal mesh-pattern filter and a transparent conductive film filter. Although the metal mesh-pattern filter exhibits a good electromagnetic wave shielding effect, it has several disadvantages including poor transmittance, image distortion, and an increase in the production cost due to a costly mesh.
Due to such disadvantages, electromagnetic wave shielding filters using transparent conductive films using indium tin oxide (ITO) are being widely used instead of the metal mesh-pattern filter. The transparent conductive film is generally formed of a multi-level thin film structure in which a metal film and a high-refractive-index transparent thin layer are sandwiched. Silver or a silver-based alloy may be used as the metal film.
One example of the multi-level thin film structure for use in the conventional electromagnetic wave shielding filters is disclosed in Korean Patent Application No. 1997-20914, entitled, “Transparent Laminate and Optical Filter for Display Using Same,” filed in May 27, 1997.
The disclosed technology has a sequentially and alternately stacked structure of three thin layers comprised of silver or a silver alloy and three high-index-refractive transparent, thin layers. Here, the high-refractive-index transparent thin layers are comprised of indium oxide and the metal thin layer is comprised of silver or a silver alloy.
In conventional electromagnetic wave shielding filters using the laminate structure, decrease of sheet resistance is achieved by increasing the number of metal thin layers in the laminate structure. However, there are problems that the increase of the number of metal thin layers leads to low visible light transmittance while enhancing sheet resistance, an increase in the production cost, and low manufacturability.
Further, the conventional electromagnetic wave shielding filters have a disadvantage because the metal thin layers generally comprised of silver are vulnerable to chemicals and easily eroded. Various attempts have been made to prevent erosion of metallic thin films. However, no successful solution has yet been proposed due to some environmental factors.